更符合python的方式来编写这个块(和elimnate: ValueError: dictionary update sequence element #0的长度为1;2是必需的)

I have this (which works):

我有这个(可以用的):

def make_key(x):
    return "{0}/{1}/{2}".format(x.f1, x.f2, x.f3)

def make_value(x):
    return (x.f7, x.f1, x.f4, x.f9, 
            x.f2, x.f8, x.f10, x.f11, x.f12, x.f17, 
            x.f18, x.f19, x.f14, x.f15,
            x.f16, x.f17, x.f20)

row_data = {}
    for x in records:
        key = make_key(x.f1,x.f2,x.f3)
        value = make_value(x)
        row_data[key] = value

I tried this:

我试着这样的:

row_data = dict([(make_key(x), make_value(x))] for x in records)

I get this error:

我得到这个错误:

ValueError: dictionary update sequence element #0 has length 1; 2 is required

Edit:

编辑:

records is a list of objects that have field properties f1, ...fn

记录是具有字段属性f1，…fn的对象的列表

2 个解决方案

#1

You need to drop the list wrapper; just produce the tuples:

您需要删除列表包装;只是生产元组:

row_data = dict((make_key(x), make_value(x)) for x in records)

You were producing a list with one element each, a tuple.

您正在生成一个列表，每个元素都有一个元组。

If you are using Python 2.7 or newer, you can also use a dictionary comprehension:

如果您使用的是Python 2.7或更新版本，还可以使用字典理解:

row_data = {make_key(x): make_value(x) for x in records}

Your make_value could be expressed by using a operator.itemgetter() object:

您的make_value可以通过使用operator.itemgetter()对象来表示:

from operator import itemgetter

make_value = itemgetter(
    'f7', 'f1', 'f4', 'f9', 'f2', 'f8', 'f10', 'f11', 'f12', 'f17', 
    'f18', 'f19', 'f14', 'f15', 'f16', 'f17', 'f20')

The make_key() function can make use of the fact that you can pull out attributes from an object; {0.f1} would interpolate the f1 attribute of the first positional argument to the str.format() method; make use of this to create a bound str.format() method that takes just one positional argument:

make_key()函数可以利用从对象中提取属性的事实;{ 0。f1}将第一个位置参数的f1属性插入到string .format()方法;使用这个方法创建一个绑定的str.format()方法，它只需要一个位置参数:

make_key = '{0.f1}/{0.f2}/{0.f3}'.format

#2

A few different things you can do to make it simpler :)

你可以做一些不同的事情来简化它:)

No need for a separate make_key function definition, you already have one:

不需要单独的make_key函数定义，您已经有了一个:

make_key = '{0.f1}/{0.f2}/{0.f3}'.format

Beyond that, depending on your Python version you can also use dict comprehensions:

除此之外，根据您的Python版本，您还可以使用字典理解:

row_data = {make_key(x): make_value(x) for x in records}

#1